episode 123 "Ichigo, complete hollowification!?"
Think ying and yang. Ichigo's inner self his doppelganger carries spirit power of a hollow equal to that of the Shinigami side, a mirror opposite. Two sides fighting over control - The king and the horse. Ichigo's battle is not simply to be the king but also to work in unity with his other half to gain full use of his hollow power. Since each side of Ichigo is equal or above captain level the full use of both powers would be...awesome.

I actually just found out that people call hollow ichigo Hichigo today -_- how much do I fail as a bleach fan? I hadn't really thought of his name before, because I just thought he was Ichigo's hollow version.. wierd! The backwards/upside down thing is really cool though!